Apple took a lot of heat over their UDID system earlier this year when it was discovered that some developers were misusing the information. And the criticism amplified a few weeks ago when hackers published a list of over a million device IDs.

In response to the hack, Apple released a statement saying that it was going to be replacing the UDID in iOS 6, and was banning the future use of the data. That replacement is called Advertising Identifier, and Apple introduces it in iOS 6 GM…

“iOS 6 introduces the Advertising Identifier, a non-permanent, non-personal, device identifier, that advertising networks will use to give you more control over advertisers’ ability to use tracking methods. If you choose to limit ad tracking, advertising networks using the Advertising Identifier may no longer gather information to serve you targeted ads. In the future all advertising networks will be required to use the Advertising Identifier. However, until advertising networks transition to using the Advertising Identifier you may still receive targeted ads from other networks.”

The new identifier is obviously targeted toward advertisers, so it’s unclear if Apple will allow developers to access this, or similar, data. It’s also not clear when exactly Apple will start forcing ad networks to use the new system, as it’s UDIDs until then.